Part of football's beauty can be sourced in its unpredictability. It's a volatile arena in which things can turn for better or worse pretty quickly and where few things go to plan. It makes room for surprises, revelations and unforeseen turns.
Here, we celebrate some of those surprises, checking in on 15 of Europe's biggest clubs and bringing you their revelations of the season. Each has a player who has exceeded expectations, shot from nowhere to be a factor or settled so fast it's shocked you.
AC Milan: Patrick Cutrone Emerges from the Depths
Football works in strange ways.
AC Milan's summer of heavy spending touched all areas of the squad and, in particular, narrowed in on a striking corps severely lacking in troops. Andre Silva (£35 million) and Nikola Kalinic (loan, then £22 million) were brought in, but the forward who immediately stole the show was one already in situ: youth product Patrick Cutrone.
With Silva a late arrival because of the FIFA Confederations Cup, Carlos Bacca departed and Kalinic a late buy, Cutrone was the only forward at the club while they played their early UEFA Europa League qualifying matches.
He impressed, showing great movement and goalscoring instincts, and he has made an impact on this fledgling Serie A season, too, scoring against Crotone and Cagliari. The Rossoneri's participation in the Europa League should ensure manager Vincenzo Montella continues to give him minutes.
Arsenal: Sead Kolasinac Is a Star
Arsenal fans knew they were getting a good player in Sead Kolasinac, as he arrived with the pedigree of more than 100 Schalke 04 games and a 2016-17 Bundesliga Team of the Season nomination under his belt.
But the sheer impact he can have on games was perhaps not expected. His ox-like frame has given Arsenal a new edge in attack and defence, and whenever he's played, he's been excellent.
Why manager Arsene Wenger felt the need to drop him (and Alexandre Lacazette) for the visit to Liverpool at the end of August, no one knows. Why would you drop your best player (this season) for the biggest game yet?
Atletico Madrid: Thomas Partey Being a Factor
Atletico Madrid's restrictions in the transfer market this summer were well-known, and boss Diego Simeone has been forced to lean on his existing crop for at least the first half of the 2017-18 season.
He had to be careful with how many players he sold off so he didn't find himself short, and that's perhaps given Thomas Partey the chance no one thought would come: to play consistently in this team for a period and show what he's made of.
The beginning of this campaign has been a grind for Atletico, with four of their first five games taking place away from home, but the results have been good. Thomas, who has started all but one of their matches, has been a positive force.
Barcelona: Nelson Semedo Catching Fire
Nelson Semedo's acquisition was somewhat overshadowed by the Neymar saga; with the walls supposedly falling down around Barcelona, the signing of a Portuguese right-back simply did not register with some.
He came with a reasonable reputation, being one of several talented players Benfica let go this summer, and he wasn't cheap at £26.5 million. Still, he wasn't expected to settle so quickly and offer so much so soon.
He's upgraded the right flank tangibly, solving what has been a problematic position for several years. It means no manager should be tempted to try that strange lopsided diamond former boss Luis Enrique used at the back end of last season and that Ivan Rakitic and Sergi Roberto won't be fielded in hybrid CM/RWB roles.
Bayern Munich: Joshua Kimmich Exceeding All Expectations
Losing Philipp Lahm and Xabi Alonso—two very talented players but also two leaders—in one summer was expected to hit Bayern Munich hard. The holes their departures left were huge.
The club dipped into the transfer market to retool the midfield, signing Corentin Tolisso from Olympique Lyonnais, but they looked in-house to replace Lahm, transitioning Joshua Kimmich to right-back on a permanent basis. He'd already played there at times and impressed there for Germany at UEFA Euro 2016, but growing pains were still expected.
To be frank, there have barely been any. Kimmich's offensive input has been monstrous—he managed four assists in one week earlier in September—and he's been fairly stable defensively, too. He's exceeding all expectations in this new role already.
Borussia Dortmund: Nuri Sahin the Conductor
Sure, injuries have played a part here (particularly Julian Weigl's), but by a show of hands, who expected Nuri Sahin to be a key part of any Borussia Dortmund midfield at this point?
The Black and Yellows have been the best team in the Bundesliga in 2017-18, top the table and have yet to concede a goal across five league matches. Their midfield play has been incredible, and Sahin is conducting things from a deep-lying role.
He's totalled the most passes completed (378) of any midfielder in Germany, already has a goal and an assist to his name and is holding the fort magnificently whilst BVB's long list of injuries clears up.
Chelsea: Charly Musonda Is Born
The odds-on favourite to transition from Chelsea academy to first team changes pretty violently. Multiple players have had moments in the sun (Dominic Solanke and Ruben Loftus-Cheek are but two), but none have stuck.
That's what Charly Musonda will be hoping to change, and if he's given the chance to build on his fantastic display against Nottingham Forest in the Carabao Cup, there's every chance he will.
An uber-talented, versatile midfielder, the Belgian has been kept at the club this season (rather than left on loan) because manager Antonio Conte clearly believes in him. Let's see if he can repay that faith.
Juventus: Daniele Rugani Is Already the Best Option Beside Giorgio Chiellini
That Daniele Rugani is a good player and a potentially elite central defender is not news. He's been in position, waiting for one of Giorgio Chiellini or Leonardo Bonucci to depart or decline, for two years, and so this summer he took the step that had always been planned for him.
But what has surprised many is how quickly he has become the clear and obvious first-choice option to partner Chiellini. When he's missing, Juve fans are concerned—despite having stand-ins such as Medhi Benatia, Andrea Barzagli and Benedikt Howedes.
Rugani is doing what was always expected of him—only much quicker than anyone anticipated.
Liverpool: Joe Gomez, Not Trent Alexander-Arnold
Plenty has been made of Trent Alexander-Arnold's presence in Liverpool's team this year, and there's no doubt he's a wonderful talent who will simply get better and better.
But most of his first-team appearances have seen him struggle—his outings against Hoffenheim at Anfield, Watford and Burnley are particularly noteworthy—and it's Joe Gomez's return that has brought stability to Liverpool's right side in the absence of Nathaniel Clyne.
A forgotten man because of successive long-term injuries, the former Charlton Athletic defender has performed well when called upon and memorably shone in the 4-0 destruction of Arsenal. Alexander-Arnold is getting all the praise, but Gomez is the revelation in red.
Manchester City: John Stones Taking the Leap
What we've seen from Manchester City this season is largely exactly what was expected.
Following a summer overhaul at full-back, Pep Guardiola's attacking template fits the squad better, and he's getting far more out of them. The strikers are purring, the midfield is dominating and the clean-sheet potential is much improved following the acquisition of a great goalkeeper in Ederson Moraes.
But one surprise has been the excellent play of John Stones, who has clearly spent the summer working hard on his game and is consequently reaping the benefits. His passing is more dangerous than ever, and as a covering centre-back in a high line, he's finding his niche.
Concerns were aired over City's inability to procure another centre-back during the transfer window, but Stones' slightly unexpected leap has put those to bed fast.
Manchester United: Phil Jones' Dominance
It may not last, so Manchester United fans are simply enjoying it while they can. Phil Jones has started 2017-18 as if he has a point to prove, and his great performances have made leaving summer signing Victor Lindelof out of the team an easy choice.
Strong, deceptively fast and willing to tussle for the ball, he's been like a slightly lesser Eric Bailly, and together they have represented two Terminators, charging about and snuffing out danger.
We know Jones is likely to lose form soon, probably because of injury (a problem he's had throughout his career). And if that does happen, United will be weaker for it.
Not many people would have thought that would be the case before the season began.
Monaco: Jorge Will Be Fine
AS Monaco's recruitment is among the best in the world, and you have to give it to them: They have judged their left-back situation superbly.
Back in January, they signed Jorge from Flamengo for £7.5 million but barely played him. He sat on the bench for six months, learning and adapting, while Benjamin Mendy stole the show and drove his transfer fee through the roof.
With Mendy sold (for £52 million), Jorge has stepped in, and he's started regularly and played well. They are by no means the same kind of presence on the pitch, but he's a solid option who removes any worry over the position.
Paris Saint-Germain: Neymar Is Out of this World
We didn't have anywhere to go for Paris Saint-Germain other than in the direction of Neymar. He and Kylian Mbappe aside, it's the same nine guys from last season, and they're dominating in the way you would expect them to.
It's been nice to see Giovani Lo Celso get some game time off the bench, but his 41 minutes over four league appearances aren't worth singing about.
So to Neymar we go, and the truth is, in spite of his reputation as one of the world's best players, he's still managed to wow us. We all knew he was world class and inexplicably excellent, yet he still has us applauding and flocking to watch him.
Many fans are watching more Ligue 1 than they have in the past, and it's because of one man.
Real Madrid: Borja Mayoral to the Rescue
Options for Real Madrid's revelation were limited, but then Borja Mayoral rode through like a knight in shining armour to rescue us.
The 20-year-old impressed immensely on his first appearance for Los Blancos this season, netting and forcing a second against Real Sociedad on Sunday. All of the linkup prowess and clever movement he flashed at youth level came through on the senior stage.
Given Karim Benzema's proneness to injury and the fact Real Madrid sold backup striker Alvaro Morata in the summer, Mayoral's breakthrough is of the most welcome kind.
Tottenham: Davinson Sanchez Slotting In Seamlessly
There are few things worse for a manager to deal with than an expensive signing's struggles to adapt early and consequent errors—especially in the defensive area. Media and fan pressure begins to build, and it can throw a player off his game and set him back months.
With that in mind, Tottenham Hotspur boss Mauricio Pochettino will be extremely relieved Davinson Sanchez has taken to Premier League life like a duck to water. He cost a club-record fee of £38 million in the summer and entered a defence that conceded the fewest goals in the division in 2016-17, so the risks were high.
But Sanchez has filled the space between the high defensive line and Hugo Lloris well, utilising his blinding speed to track back. There has been no adaptation time for a 21-year-old playing in a new league without any real knowledge of the language. Impressive.
All statistics via WhoScored.com